I. Field of the Invention
This invention relates to a cleaning device, and in particular, to a cleaning device for cleaning the writing heads used in ink jet recorders and printers.
II. Statement of the Prior Art
Typically, in an ink jet recorder or printer, the ink is pumped under pressure to a manifold having one or more openings or orifices through which the ink is forced onto a recording surface. For example, in an ink jet printer there is provided a rapid and quiet method of printing with tiny drops of ink. During ink jet printing, the ink drops are ejected from hundreds of orifices having diameters typically less than 0.003 inches in an ink head which is closely spaced (commonly of the order of 1 to 1.5 mm for impulse ink jets, but larger distances for continuous ink jets) from the record medium on which characters or other information is to be printed. The characters are formed by small ink drops which, depending upon a variety of well-known factors such as the ink and paper, result in varying degrees of printing quality. It is, of course, critical to the proper operation of an ink jet recorder or printer that the openings through which the ink passes remain clean and unobstructed. However, it has been found that this is not an easy objective to accomplish. For example, the exit area of the openings on the ink head tend to attract particles or impurities from the surrounding atmosphere which interfere with the flow of the ink through the openings. The ink itself tends to thicken or completely dry around the openings thereby interfering with the formation of perfectly straight ink drop streams flowing from the opening. The accumulation of dried ink or atmospheric impurities at the openings can also lead to the formation of air bubbles in the ink jet head orifices which in turn will cause the ink jet head to malfunction.
Many different attempts have been made to solve the above outlined problems by either providing various types of cleaning compositions which are added to the ink itself or securing a cleaning device to the ink jet apparatus. For example, U.S. Pat. No. 4,256,610 discloses an aqueous based composition used for removing ink residues and other foreign matter from the orifices and other fluid areas of an ink jet recording apparatus. U.S. Pat. Nos. 4,007,465 and 4,050,078 describes various mechanical systems for cleaning ink jet heads.
In U.S. Pat. No. 4,112,435, there is described a mechanical device in the form of a shield and wiper for cleaning ink jet recording devices. The device consists of a shield member mounted on the writing head and movable between a blocking position in front of the orifices of the writing head and an operating position spaced from and clear of the orifices. The shield is equipped with a resilient wiping arm which wipes across the face of the writing head during movement between the positions. One problem with this type of device is that it cleans by a squeeze action which can leave a film of ink on the writing head that can interfere with the subsequent firing of the ink jets. It is also possible with this type of squeeze action to draw ink out of the orifices of the writing head which would add to the ink left behind in the form of a film and therefore further interfere with the firing of the heads. The ink removed by the cleaner described in this patent falls by gravity away from the writing head. This limits using the heads in a horizontal position since to position the heads vertically would allow ink to creep back into the orifices. Furthermore, removing the excess ink in this manner allows the ink to get on other portions of the machine which is not very desirable. In addition, this type of cleaning device will work primarily on a flat surface. It would therefore require a careful alignment procedure.
U.S. Pat. No. 4,223,322 discloses a device for cleaning an ink writing head in an ink printer. The device includes a liquid absorbing cleaning medium in the form of a movable tape supported between two reels. The tape is brought into contact with the orifices in the ink writing head to permit ink to flow from the nozzles to the cleaning medium to be absorbed by the medium. In this type of device the ink is absorbed into the cleaning medium with no specific control as to how the ink spreads. To thereby adequately remove all the ink a large cleaning surface area of non-reusable material is used. This system is further limited in that it cannot be used for cleaning irregularly shaped surfaces. Furthermore, as a cleaner, the device is relatively complicated in design having several moving parts and is therefore more prone to failure and relatively expensive.